Yes it starts in January but I mentioned March because it took some time for a large number of people to actually get the vaccine, and also there was probably f

Yes it starts in January but I mentioned March because it took some time for a large number of people to actually get the vaccine, and also there was probably flu going around in Jan/Feb. I should have said July not August. The numbers reflect weekly, age standardised death rates. Therefore once you have a decent population size in each cohort, the timing shouldn’t matter. These are non-covid deaths so rates shouldn’t change except for normal seasonal patterns. However it could be something like what JoshuaDavid mentions below - that healthy people are disproportionately being moved from the 21 days cohort to the second dose cohort by some selection mechanism.